Vaso-occlusive device delivery system

ABSTRACT

A vaso-occlusive device delivery assembly includes a pusher assembly and a vaso-occlusive device detachably coupled to the pusher assembly by an attachment member is frictionally secured within a lumen of the pusher assembly. A heat generating member is disposed in the pusher assembly lumen, along with a pressure generating material, such that, when heat is generated by the heat generative device, the pressure generating material increases a pressure in the pusher assembly lumen, thereby dislodging the attachment member from the pusher assembly and detaching the vaso-occlusive device from the pusher assembly.

RELATED APPLICATION DATA

The present application is a continuation of pending U.S. patentapplication Ser. No. 14/206,244, filed Mar. 12, 2014, issued as U.S.Pat. No. 9,451,964, which claims the benefit under 35 U.S.C. § 119 toU.S. Provisional Application Ser. No. 61/785,556, filed Mar. 14, 2013.The foregoing applications are hereby incorporated by reference into thepresent application in its entirety.

FIELD

The field of the disclosed inventions generally relates to systems anddelivery devices for implanting vaso-occlusive devices for establishingan embolus or vascular occlusion in a vessel of a human or veterinarypatient. More particularly, the disclosed inventions relate to pressureactuated vaso-occlusive device delivery systems.

BACKGROUND

Vaso-occlusive devices or implants are used for a wide variety ofreasons, including treatment of intra-vascular aneurysms. Commonly usedvaso-occlusive devices include soft, helically wound coils formed bywinding a platinum (or platinum alloy) wire strand about a “primary”mandrel. The coil is then wrapped around a larger, “secondary” mandrel,and heat treated to impart a secondary shape. For example, U.S. Pat. No.4,994,069, issued to Ritchart et al., which is fully incorporated hereinby reference as though set forth in full, describes a vaso-occlusivedevice that assumes a linear, helical primary shape when stretched forplacement through the lumen of a delivery catheter, and a folded,convoluted secondary shape when released from the delivery catheter anddeposited in the vasculature.

In order to deliver the vaso-occlusive devices to a desired site in thevasculature, e.g., within an aneurysmal sac, it is well-known to firstposition a small profile, delivery catheter or “micro-catheter” at thesite using a steerable guidewire. Typically, the distal end of themicro-catheter is provided, either by the attending physician or by themanufacturer, with a selected pre-shaped bend, e.g., 45°, 26°, “J”, “S”,or other bending shape, depending on the particular anatomy of thepatient, so that it will stay in a desired position for releasing one ormore vaso-occlusive device(s) into the aneurysm once the guidewire iswithdrawn. A delivery or “pusher” wire is then passed through themicro-catheter, until a vaso-occlusive device coupled to a distal end ofthe pusher assembly is extended out of the distal end opening of themicro-catheter and into the aneurysm. Once in the aneurysm, segments ofsome vaso-occlusive devices break off to allow more efficient andcomplete packing. The vaso-occlusive device is then released or“detached” from the end of the pusher assembly, and the pusher assemblyis withdrawn back through the catheter. Depending on the particularneeds of the patient, one or more additional occlusive devices may bepushed through the catheter and released at the same site.

One well-known way to release a vaso-occlusive device from the end ofthe pusher assembly is through the use of an electrolytically severablejunction, which is a small exposed section or detachment zone locatedalong a distal end portion of the pusher assembly. The detachment zoneis typically made of stainless steel and is located just proximal of thevaso-occlusive device. An electrolytically severable junction issusceptible to electrolysis and disintegrates when the pusher assemblyis electrically charged in the presence of an ionic solution, such asblood or other bodily fluids. Thus, once the detachment zone exits outof the catheter distal end and is exposed in the vessel blood pool ofthe patient, a current applied through an electrical contact to theconductive pusher completes an electrolytic detachment circuit with areturn electrode, and the detachment zone disintegrates due toelectrolysis.

While electrolytically severable junctions have performed well, thereremains a need for other systems and methods for delivery vaso-occlusivedevices into vessel lumens.

SUMMARY

In one embodiment of the disclosed inventions, a vaso-occlusive devicedelivery assembly includes a pusher assembly and a vaso-occlusive devicehaving an attachment member at a proximal end thereof. The pusherassembly includes an elongate body having a distal end and a pusherassembly lumen in communication with an opening in the distal end, theattachment member being frictionally secured to the pusher assemblywithin the pusher assembly lumen, such that the vaso-occlusive device isdetachably connected to the pusher assembly. A heat generating member isdisposed in the pusher assembly lumen, and a pressure generatingmaterial disposed in the pusher assembly lumen, such that, when heat isgenerated by the heat generative device, the pressure generatingmaterial increases a pressure in the pusher assembly lumen, therebydislodging the attachment member from the pusher assembly and detachingthe vaso-occlusive device from the pusher assembly.

In some embodiments, the heat generating member may be disposed in thedistal end of the elongate body, and the pressure generating materialmay be adjacent to, or in contact with, the heat generating member.Alternatively or additionally, the pressure generating material maysurround the heat generating member. The pressure generating materialmay include a solid, such as an inorganic salt hydrate, selected fromthe group consisting of sodium carbonate monohydrate, calcium sulfatedihydrate, calcium sulfate pentahydrate, copper sulfate pentahydrate,and sodium bicarbonate. At least a part of the pressure generatingmaterial, when heated, changes state, becoming a liquid or a gas.

In other embodiments, the pressure generating material includes a fluid.The pusher assembly and the vaso-occlusive device may be configured suchthat the fluid may be introduced into the pusher assembly lumen duringdelivery.

In some embodiments, the heat generating member is a resistive heatingcoil. The assembly may also include a seal disposed in the pusherassembly lumen proximal of the heat generating member such that, whenthe attachment member is frictionally secured to the pusher assemblywithin the pusher assembly lumen, the respective seal, elongate body,and attachment member define a substantially fluid tight chamber.

In some embodiments, the pusher assembly also includes a resilientretaining member frictionally secured to the attachment member withinthe pusher assembly lumen, where, when heat is generated by the heatgenerating member, the pressure generating material increases a pressurein the pusher assembly lumen, thereby deforming the resilient retainingmember and detaching the vaso-occlusive device from the pusher assembly.The retaining member may be made of a deformable polymer.

In another embodiment of the disclosed inventions, a vaso-occlusivedevice delivery assembly includes a pusher assembly and a vaso-occlusivedevice defining a vaso-occlusive device lumen. The pusher assemblyincludes an elongate body having a distal end and a pusher assemblylumen in communication with an opening in the distal end, a tubularconnecting member having an open proximal end and a closed distal end,where the open proximal end is disposed in the pusher assembly lumen atthe distal end of the elongate body, a heat generating member disposedat least partially disposed in the tubular connecting member, and apressure generating material disposed in the pusher assembly lumen. Theclosed distal end of the tubular connecting member is attached to thevaso-occlusive device in the vaso-occlusive device lumen such that thevaso-occlusive device is detachably connected to the pusher assembly viathe tubular connecting member. The pressure generating material and theheat generating member form a substantially fluid tight seal at the openproximal end of the tubular connecting member. When heat is generated bythe heat generative device, the pressure generating material increases apressure in the tubular connecting member, thereby severing the tubularconnecting member and detaching the vaso-occlusive device from thepusher assembly. In some embodiments, the pressure generating materialis disposed adjacent the heat generating member.

In some embodiments, the tubular connecting member includes a detachzone, and increasing a pressure in the tubular connecting member maysever the tubular connecting member at the detach zone. The tubularconnecting member may perforated at the detach zone to accelerateseverance of the tubular connecting member with increased pressure inthe tubular connecting member. Alternatively or additionally, the detachzone may be treated to accelerate severance of the tubular connectingmember with increased pressure in the tubular connecting member. Thedetach zone may be thermally or mechanically weakened.

In yet another embodiment of the disclosed inventions, a vaso-occlusivedevice delivery assembly includes a pusher assembly and a vaso-occlusivedevice including an attachment member at a proximal end thereof, theattachment member being secured to the pusher assembly within the pusherassembly lumen with an interference fit, such that the vaso-occlusivedevice is detachably connected to the pusher assembly. The pusherassembly includes an elongate body having a distal end and a pusherassembly lumen in communication with an opening in the distal end, and aheat generating member disposed in the pusher assembly lumen. When heatis generated by the heat generative device, the a pressure in the pusherassembly lumen increases, thereby overcoming the interference fit,dislodging the attachment member from the pusher assembly, and detachingthe vaso-occlusive device from the pusher assembly.

In still another embodiment of the disclosed inventions, a method ofdetaching a vaso-occlusive device from a pusher assembly frictionallyattached thereto includes activating a heat generating member disposedin a lumen of the pusher assembly to generate heat to cause a pressuregenerating material to generate pressure to overcome a frictionalattachment, thereby detaching the vaso-occlusive device from the pusherassembly. The generated pressure may also force the vaso-occlusivedevice away from the pusher assembly.

Other and further aspects and features of embodiments of the disclosedinventions will become apparent from the ensuing detailed description inview of the accompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings illustrate the design and utility of embodiments of thedisclosed inventions, in which similar elements are referred to bycommon reference numerals. These drawings are not necessarily drawn toscale. In order to better appreciate how the above-recited and otheradvantages and objects are obtained, a more particular description ofthe embodiments will be rendered, which are illustrated in theaccompanying drawings. These drawings depict only typical embodiments ofthe disclosed inventions and are not therefore to be considered limitingof its scope.

FIG. 1 is a schematic view of a vaso-occlusive device delivery system,according to one embodiment of the disclosed inventions.

FIGS. 2-5B are detailed longitudinal cross-sectional views ofvaso-occlusive device delivery systems according to various embodimentsof the disclosed inventions, which depict the junction between thevarious pusher assemblies and vaso-occlusive devices.

FIG. 6 is a side view of an occlusive coil in a natural state mode,illustrating one exemplary secondary configuration according to anembodiment of the disclosed inventions.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

For the following defined terms, these definitions shall be applied,unless a different definition is given in the claims or elsewhere inthis specification.

All numeric values are herein assumed to be modified by the term“about,” whether or not explicitly indicated. The term “about” generallyrefers to a range of numbers that one of skill in the art would considerequivalent to the recited value (i.e., having the same function orresult). In many instances, the terms “about” may include numbers thatare rounded to the nearest significant figure.

The recitation of numerical ranges by endpoints includes all numberswithin that range (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4,and 5).

As used in this specification and the appended claims, the singularforms “a”, “an”, and “the” include plural referents unless the contentclearly dictates otherwise. As used in this specification and theappended claims, the term “or” is generally employed in its senseincluding “and/or” unless the content clearly dictates otherwise.

Various embodiments of the disclosed inventions are describedhereinafter with reference to the figures. It should be noted that thefigures are not drawn to scale and that elements of similar structuresor functions are represented by like reference numerals throughout thefigures. It should also be noted that the figures are only intended tofacilitate the description of the embodiments. They are not intended asan exhaustive description of the invention or as a limitation on thescope of the invention, which is defined only by the appended claims andtheir equivalents. In addition, an illustrated embodiment of thedisclosed inventions needs not have all the aspects or advantages shown.An aspect or an advantage described in conjunction with a particularembodiment of the disclosed inventions is not necessarily limited tothat embodiment and can be practiced in any other embodiments even ifnot so illustrated.

FIG. 1 illustrates a known vaso-occlusive device delivery system 10. Inthe system 10 illustrated in FIG. 1, the vaso-occlusive device is avaso-occlusive coil 300. The system 10 includes a number ofsubcomponents or sub-systems. These include a delivery catheter 100, apusher assembly 200, a vaso-occlusive coil 300, and a power supply 400.The delivery catheter 100 includes a proximal end 102, a distal end 104,and a lumen 106 extending between the proximal and distal ends 102, 104.The lumen 106 of the delivery catheter 100 is sized to accommodate axialmovement of the pusher assembly 200 and the vaso-occlusive coil 300.Further, the lumen 106 is sized for the passage of a guidewire (notshown) which may optionally be used to properly guide the deliverycatheter 100 to the appropriate delivery site.

The delivery catheter 100 may include a braided-shaft construction ofstainless steel flat wire that is encapsulated or surrounded by apolymer coating. By way of non-limiting example, HYDROLENE® is a polymercoating that may be used to cover the exterior portion of the deliverycatheter 100. Of course, the system 10 is not limited to a particularconstruction or type of delivery catheter 100 and other constructionsknown to those skilled in the art may be used for the delivery catheter100. The inner lumen 106 may be advantageously coated with a lubriciouscoating such as PTFE to reduce frictional forces between the deliverycatheter 100 and the respective pusher assembly 200 and vaso-occlusivecoil 300 being moved axially within the lumen 106. The delivery catheter100 may include one or more optional marker bands 108 formed from aradiopaque material that can be used to identify the location of thedelivery catheter 100 within the patient's vasculature system usingimaging technology (e.g., fluoroscope imaging). The length of thedelivery catheter 100 may vary depending on the particular application,but generally is around 150 cm in length. Of course, other lengths ofthe delivery catheter 100 may be used with the system 10 describedherein.

The delivery catheter 100 may include a distal end 104 that is straightas illustrated in FIG. 1. Alternatively, the distal end 104 may bepre-shaped into a specific geometry or orientation. For example, thedistal end 104 may be shaped into a “C” shape, an “S” shape, a “J”shape, a 45° bend, a 90° bend. The size of the lumen 106 may varydepending on the size of the respective pusher assembly 200 andvaso-occlusive coil 300, but generally the OD of the lumen 106 of thedelivery catheter 100 (I.D. of delivery catheter 100) is less than about0.02 inches. The delivery catheter 100 is known to those skilled in theart as a microcatheter. While not illustrated in FIG. 1, the deliverycatheter 100 may be utilized with a separate guide catheter (not shown)that aids in guiding the delivery catheter 100 to the appropriatelocation within the patient's vasculature.

As illustrated in FIGS. 1 and 2, the system 10 includes a pusherassembly 200 configured for axial movement within the lumen 106 of thedelivery catheter 100. The pusher assembly 200 generally includes aproximal end 202 and a distal end 204. The pusher assembly 200 includesa pusher conduit 214, which has a proximal tubular portion 206 and adistal coil portion 208, and defines a pusher lumen 212 and a distalopening 218 in communication with the pusher lumen 212.

FIG. 2 illustrates a detailed longitudinal cross-sectional view of thejunction 250 between the pusher assembly 200 and the vaso-occlusive coil300 according to one embodiment of the disclosed inventions. Similarelements of this embodiment are identified with the same referencenumbers as discussed above with respect to FIG. 1. The pusher assembly200 includes a proximal end 202 and a distal end 204 and measuresbetween around 184 cm to around 186 cm in length. The proximal tubularportion 206 may be formed from, for example, a flexible stainless steelhypotube. The proximal tubular portion 206 may be formed from stainlesssteel hypotube having an OD of 0.01325 inches and inner diameter (ID) of0.0075 inches. The length of the hypotube section may be between around140 cm to around 150 cm, although other lengths may also be used.

A distal coil portion 208 is joined in end-to-end fashion to the distalface of the proximal tubular portion 206. The joining may beaccomplished using a weld or other bond. The distal coil portion 208 mayhave a length of around 39 cm to around 41 cm in length. The distal coilportion 208 may comprise a coil of 0.0025 inches×0.006 inches. The firstdimension generally refers to the OD of the coil wire that forms thecoil. The latter dimension generally refers to the internal mandrel usedto wind the coil wire around to form the plurality of coil winds and isthe nominal ID of the coil. One or more windings of the distal coilportion 208 may be formed from a radiopaque material, forming markercoils. For example, the distal coil portion 208 may include a segment ofstainless steel coil (e.g., 3 cm in length), followed by a segment ofplatinum coil (which is radiopaque and also 3 mm in length), followed bya segment of stainless steel coil (e.g., 37 cm in length), and so on andso forth.

An outer sleeve 232 or jacket surrounds a portion of the proximaltubular portion 206 and a portion of the distal coil portion 208 of thepusher conduit 214. The outer sleeve 232 covers the interface or jointformed between the proximal tubular portion 206 and the distal coilportion 208. The outer sleeve 232 may have a length of around 50 cm toaround 54 cm. The outer sleeve 232 may be formed from a polyether blockamide plastic material (e.g., PEBAX 7233 lamination). The outer sleeve232 may include a lamination of PEBAX and HYDROLENE® that may be heatlaminated to the pusher assembly 200. The OD of the outer sleeve 232 maybe less than 0.02 inches and advantageously less than 0.015 inches. Inembodiments where the pusher conduit 214 forms the negative conductor222, the outer sleeve 232 is removed from the very distal end of thepusher conduit 214, during manufacturing, to form an exposed negativeelectrical contact 224.

As shown in FIG. 2, the pusher assembly 200 further includes a heatgenerating member 210 disposed in its distal end 204. In the embodimentdepicted in FIG. 2, the heat generating member 210 is a resistiveheating coil 210. In other embodiments, the heat generating member 210may include mechanical, inductive, magnetic, or optical mechanisms. Theresistive heating coil 210 is connected to positive and negativeconductors 220, 222 disposed in the pusher lumen 212. The resistiveheating coil 210 can be wound from Nichrome® (nickel chromium alloy)wire, such that when a current is delivered through the resistiveheating coil 210 by the positive and negative conductors 220, 222 fromthe power supply 400, a resistance to the current flow generates heat inthe resistive heating coil 210.

The positive and negative conductors 220, 222 may be formed from anelectrically conductive material such as copper wire, with an OD ofaround 0.00175 inches. The proximal ends of the positive and negativeconductors 220, 222 are electrically connected to positive and negativeelectrical contacts 216, 224, respectively. As shown in FIG. 1, positiveand negative electrical contacts 216, 224 are located at the proximalend of the pusher assembly 200. The positive electrical contact 216 maybe formed from a metallic solder (e.g., gold) that is configured tointerface with a corresponding electrical contact (not shown) in thepower supply 400 (described below). The negative electrical contact 224may be an annular ring electrode disposed on top of an electricallyinsulative outer sleeve 232 at the proximal end of the pusher conduit214 (described below). The positive and negative conductors 220, 222 maybe coated with an insulative coating such as polyimide except where theyconnect to the positive and negative electrical contacts 216, 224,respectively.

The resistive heating coil 210 is substantially surrounded by a pressuregenerating material 226. In some embodiments, the pressure generatingmaterial 226 is a solid 226 a that becomes a liquid or a gas 226 b whenheated, thereby increasing the pressure in its immediate vicinity. Inother embodiments, the pressure generating materials 226 may be liquidsor gases. In fact, heating the air adjacent to the resistive heatingcoil 210 will increase its pressure.

Suitable pressure generating materials 226 include inorganic salthydrates. The following pressure generating materials 226 release liquidwater and water vapor at the indicated temperatures:

sodium carbonate monohydrate (Na₂CO₃.H₂O) at 100° C.,

calcium sulfate dihydrate (CaSO₄.2H₂O) at 80° C.,

copper sulfate pentahydrate (CuSO₄.5H₂O) at 100° C., and

sodium bicarbonate (NaHCO₃) at 100° C.-200° C.

Sodium bicarbonate releases water vapor and carbon dioxide gas,according to the following reaction: 2NaHCO₃ (s)→CO₂ (g)+H₂O (g)+Na₂CO₃(s). Other substances can also release oxygen gas. The gases producedmay be minimal in quantity and readily absorbable in blood.

A proximal seal 230 is also attached to the interior surface of thepusher conduit 214 in the pusher lumen 212. The proximal seal 230 islocated proximal of the resistive heating coil 210. The positive andnegative conductors 220, 222 extend through the proximal seal 230 whilethe proximal seal 230 maintains a substantially fluid tight seal betweenregions proximal and distal of the proximal seal 230.

The vaso-occlusive coil 300 includes a proximal end 302, a distal end304, and a lumen 306 extending there between. The vaso-occlusive coil300 is made from a biocompatible metal such as platinum or a platinumalloy (e.g., platinum-tungsten alloy). The vaso-occlusive coil 300includes a plurality of coil windings 308. The coil windings 308 aregenerally helical about a central axis disposed along the lumen 306 ofthe vaso-occlusive coil 300. The vaso-occlusive coil 300 may have aclosed pitch configuration as illustrated in FIGS. 1 and 2. A tether(not shown), such as a suture, may extend from the proximal end 302through the lumen 306 to the distal end 304 where it is connected to thedistal end 304 of the vaso-occlusive coil 300.

The vaso-occlusive coil 300 generally includes a straight configuration(as illustrated in FIG. 1) when the vaso-occlusive coil 300 is loadedwithin the delivery catheter 100. Upon release, the vaso-occlusive coil300 generally takes a secondary shape which may includethree-dimensional helical configurations. FIG. 6 illustrates oneexemplary configuration of a vaso-occlusive coil 300 in a natural state.In the natural state, the vaso-occlusive coil 300 transforms from thestraight configuration illustrated in, for instance, FIG. 1 into asecondary shape. The secondary shaped may include both two and threedimensional shapes of a wide variety. FIG. 6 is just one example of asecondary shape of a vaso-occlusive coil 300 and other shapes andconfigurations are contemplated to fall within the scope of thedisclosed inventions. Also, the vaso-occlusive coil 300 may incorporatesynthetic fibers (not shown) over all or a portion of the vaso-occlusivecoil 300 as is known in the art. These fibers may be attached directlyto coil windings 308 or the fibers may be integrated into thevaso-occlusive coil 300 using a weave or braided configuration. Ofcourse, the system 10 described herein may be used with occlusive coils300 or other occlusive structures having a variety of configurations,and is not limited to occlusive coils 300 having a certain size orconfiguration.

The vaso-occlusive coil 300 depicted in FIG. 2 includes an attachmentmember 310 edits proximal end 302. The attachment member 310 hasproximal and distal portions 312, 314. The attachment member 310 may bemolded from a deformable polymer. The distal portion 314 of theattachment member 310 is permanently attached to an interior surface ofthe vaso-occlusive coil 300 at the proximal end of the occlusive coillumen 306. The distal portion 314 of the attachment member 310 may beattached to the occlusive coil with an adhesive.

The proximal portion 312 of the attachment member 310 is detachablyconnected (i.e., releasably attached) to an interior surface of thepusher conduit 214 with an interference fit at the distal end of thepusher lumen 212. The proximal portion 312 of the attachment member 310has a cross-sectional area slightly larger than the cross-sectional areaof the pusher lumen 212 at its distal end. The deformability of theattachment member 310 and the relative sizes of the proximal portion 312and the pusher lumen 212 allow the proximal portion 312 to be radiallyand elastically compressed one inserted into the pusher lumen 212,thereby generating a radially outward force against the interior surfaceof the pusher conduit 214.

As shown in FIG. 2, the proximal seal 230, the proximal portion 312 ofthe attachment member 310, and the portion of the pusher conduit 214therebetween form a substantially fluid-tight pressure chamber 234.

As shown in FIG. 1, the system 10 further includes a power supply 400for supplying direct current to the positive and negative conductors220, 222. Activation of the power supply 400 causes electrical currentto flow in a circuit including the positive and negative conductors 220,222 and the resistive heating coil 210. The power supply 400 preferablyincludes an onboard energy source, such as batteries (e.g., a pair ofAAA batteries), along with drive circuitry 402. The drive circuitry 402may include one or more microcontrollers or processors configured tooutput a driving current. The power supply 400 illustrated in FIG. 1includes a receptacle 404 configured to receive and mate with theproximal end 202 of the delivery wire assembly 200. Upon insertion ofthe proximal end 202 into the receptacle 404, the positive, negativeelectrical contracts 216, 224 disposed on the delivery wire assembly 200electrically couple with corresponding contacts (not shown) located inthe power supply 400.

A visual indicator 406 (e.g., LED light) is used to indicate when theproximal end 202 of delivery wire assembly 200 has been properlyinserted into the power supply 400. Another visual indicator 420 isactivated if the onboard energy source needs to be recharged orreplaced. The power supply 400 includes an activation trigger or button408 that is depressed by the user to apply the electrical current to theresistive heating coil 210 via the positive and negative conductors 220,222. Once the activation trigger 408 has been activated, the drivercircuitry 402 automatically supplies current. The drive circuitry 402typically operates by applying a substantially constant current, e.g.,around 50-250 mA. A visual indicator 412 may indicate when the powersupply 400 is supplying adequate current to the resistive heating coil210.

In use, the vaso-occlusive coil 300 is attached to the pusher assembly200 at junction 250. The attached vaso-occlusive coil 300 and pusherassembly 200 are threaded through the delivery catheter 100 to a targetlocation (e.g., an aneurysm) in the patient's vasculature. Once thedistal and 304 of the vaso-occlusive coil 300 reaches the targetlocation, the vaso-occlusive coil 300 is pushed further distally untilit's completely exits the distal and 104 of the delivery catheter 100.

In order to detach the vaso-occlusive coil 300 from the pusher assembly200, the power supply 400 is activated by depressing the trigger 408.The drive circuitry 402 in the power supply 400 applies a current to thepositive and negative conductors 220, 222 through the positive andnegative electrical contacts 216, 224. As the applied current travelsthrough the resistive heating coil 210, the resistive heating coil 210generates heat. The generated heat raises the temperature of thepressure generating material 226 to the temperature at which it changesphases from solid 226 a liquid and/or a gas 226 b. The phase change andincreased temperature increases the pressure inside of the substantiallyfluid-tight pressure chamber 234 defined by the proximal seal 230, theproximal portion 312 of the attachment member 310, and the portion ofthe pusher conduit 214 therebetween.

When the pressure inside of the pressure chamber 234 is sufficient toovercome the friction between the proximal portion 312 of the attachmentmember 310 and the proximal end of the pusher conduit 214, theattachment member 310 and the vaso-occlusive coil 300 attached theretoare ejected from the pusher assembly 200. This positive thrust forceseparating the vaso-occlusive coil 300 from the pusher assembly 200ensures separation and prevents “sticky coils.” The liquids and gasesgenerated during detachment are readily and harmlessly absorbed into theblood.

The vaso-occlusive device delivery system 10 depicted in FIG. 3 is verysimilar to the system 10 depicted in FIG. 2. Similar elements of thisembodiment are identified with the same reference numbers as discussedabove with respect to FIG. 2. The difference between the systems 10depicted in these figures is the retention mechanism for thevaso-occlusive coil 300. The proximal portion 312 of the attachmentmember 310 depicted in FIG. 3 has a cross-sectional area smaller thanthe cross-sectional area of the pusher lumen 212.

In the system 10 depicted in FIG. 3, the proximal portion 312 includes aspherical member 316 connected to a stem 318. The spherical member 316can be made of a non-compressible material. The pusher assembly 200 alsoincludes a wedge 236 attached to an interior surface of the pusherconduit 214 in a distal end of the pusher lumen 212. The wedge 236 isalso disposed between the spherical member 316 the interior surface onthe of the pusher conduit 214. The wedge 236 can be made of a deformablepolymer and can frictionally secure the spherical member 316, theattachment member 310, and therefore the vaso-occlusive coil 300 to thepusher assembly 200.

When the resistive heating coil 210 is activated as described above,pressure builds in the substantially fluid tight pressure chamber 234defined in this embodiment by the proximal seal 230, the sphericalmember 316, the wedge 236, and the pusher conduit 214 therebetween. Theincreased pressure deforms the wedge 236 and ejects the spherical member316 from the pusher assembly 200, as also described above. Ejecting thespherical member 316 detaches the vaso-occlusive coil 300 from thepusher assembly 200 with a thrust force.

The vaso-occlusive device delivery system 10 depicted in FIG. 4 issimilar to the systems 10 depicted in FIGS. 2 and 3. Similar elements ofthis embodiment are identified with the same reference numbers asdiscussed above with respect to FIGS. 2 and 3. The embodiment depictedin FIG. 4 has different retention and detachment mechanisms than thosedepicted in FIGS. 2 and 3. The vaso-occlusive coil 300 and pusherassembly 200 are attached by a tubular member 238 having an openproximal end 240 and a closed distal end 242. The tubular member 238 ispart of the pusher assembly 200. The tubular member 238 forms a bore andmay be made from polymers, metals, alloys and ceramics.

The open proximal end 240 of the tubular member 238 is disposed in thedistal end of the pusher lumen 212 around the resistive heating coil 210and the pressure generating material 226, effectively closing theproximal end 240 of the tubular member 238. The open proximal end 240 ofthe tubular member 238 may be attached to the pusher assembly 200 viathe pusher conduit 214. The closed distal end 242 of the tubular member238 is attached to the vaso-occlusive coil 300 in the proximal end ofthe vaso-occlusive coil lumen 306. While the closed distal end 242 ofthe tubular member 238 is attached to the vaso-occlusive coil 300, thetubular member 238 remains part of the pusher assembly 200.

The tubular member 238, the resistive heating coil 210, and the pressuregenerating material 226 form a substantially fluid-tight pressurechamber 234. When the resistive heating coil 210 is activated asdescribed above, pressure builds in the pressure chamber 234,bursting/severing the tubular member 238 and detaching thevaso-occlusive coil 300 from the pusher assembly 200 with a positivethrust force. Optionally, a detachment zone 244 between the proximal anddistal ends 240, 242 of the tubular member 238 may be treated tofacilitate severing of the tubular member 238. In the embodimentdepicted in FIG. 4, the detachment zone 244 is perforated. In otherembodiments, the detachment zone 244 may be either thermally ormechanically treated to facilitate detachment.

The embodiment depicted in FIGS. 5A and 5B is similar to the system 10depicted in FIG. 4. Similar elements of this embodiment are identifiedwith the same reference numbers as discussed above with respect to FIG.4. The embodiment depicted in FIGS. 5A and 5B has different retentionand detachment mechanisms than that depicted in FIG. 4. Like theembodiment depicted in FIG. 4, the vaso-occlusive coil 300 and pusherassembly 200 are attached by a tubular member 238, which is part of thepusher assembly 200. However, the tubular member 238 has proximal anddistal ends 240, 242 that are both open and there is no solid pressuregenerating material surrounding the resistive heating coil 210.

The open proximal end 240 is disposed in the distal end of the pusherlumen 212 around the resistive heating coil 210 and the proximal seal230, effectively closing the proximal end 240. The open distal end 242is attached to the vaso-occlusive coil 300 in the proximal end of thevaso-occlusive coil lumen 306. The open distal end 242 is also disposedaround an adapter 320, effectively closing the distal end 242.

The outer sleeve 232 extends distally beyond the distal coil portion 208of the pusher conduit 214, almost making contact with vaso-occlusivecoil 300. The distal end of the outer sleeve 232 the tubular member 238and the distal end of the coil portion 208 form an annular space 246with a small opening 248 therein. The small opening 248 connects theannular space with the environment exterior to the system 10. Duringdelivery, a fluid (i.e., pressure generating material) 226 flows throughthe small opening 248 into the annular space 246. As the resistiveheating coil 210 generates heat, the fluid 226 in the annular space 246rapidly expands and/or undergoes a phase change becoming a gas. Thisincreases the pressure in the annular space and severs the tubularmember 238, thereby releasing the vaso-occlusive coil 300 from thepusher assembly 200 with positive thrust force (FIG. 5B).

The resistive heating coil 210 can also thermally degrade the tubularmember 238, facilitating severance thereof. This thermal degradation isdescribed in co-owned application Ser. No. 61/785,148, filed Mar. 14,2013 also entitled “Vaso-Occlusive Device Delivery System”. The contentsof the application Ser. No. 61/785,148 are fully incorporated herein byreference as though set forth in full. Further, the proximal seal 230,the adapter 320, and the tubular member 238 therebetween form asubstantially fluid-tight pressure chamber 234 separate from the annularspace 246. When the resistive heating coil 210 generates heat, air inthe pressure chamber 234 expands and facilitates severance of thetubular member 238.

Although particular embodiments of the disclosed inventions have beenshown and described herein, it will be understood by those skilled inthe art that they are not intended to limit the present inventions, andit will be obvious to those skilled in the art that various changes andmodifications may be made (e.g., the dimensions of various parts)without departing from the scope of the disclosed inventions, which isto be defined only by the following claims and their equivalents. Thespecification and drawings are, accordingly, to be regarded in anillustrative rather than restrictive sense. The various embodiments ofthe disclosed inventions shown and described herein are intended tocover alternatives, modifications, and equivalents of the disclosedinventions, which may be included within the scope of the appendedclaims.

What is claimed is:
 1. A vaso-occlusive device delivery assembly,comprising: a pusher assembly including a substantially fluid tightpressure chamber in a distal end portion thereof; a thermally activatedpressure generating material disposed in the pressure chamber; a heatgenerating member at least partially disposed in the pressure chamber,the heat generating member substantially surrounded by the pressuregenerating material; and a vaso-occlusive device detachably coupled tothe pusher assembly distal of the pressure chamber, wherein the pressuregenerating material comprises a solid that is configured for changingstate into, or otherwise releasing at least one of, a liquid or a gasthat increases a pressure in the pressure chamber, thereby detaching thevaso-occlusive device from the pusher assembly, in direct response toheat generated by the heat generating member, wherein the vaso-occlusivedevice comprises an attachment member at a proximal end thereof, theattachment member being frictionally secured to the pusher assembly,wherein a proximal end of the attachment member comprises a distal wallof the pressure chamber, such that the increased pressure in thepressure chamber expels the attachment member from the pusher assembly.2. The vaso-occlusive device delivery assembly of claim 1, the pusherassembly further comprising a resilient retaining member frictionallysecured to the attachment member, wherein the increased pressure deformsthe resilient retaining member.
 3. The vaso-occlusive device deliveryassembly of claim 2, wherein the resilient retaining member is made of adeformable polymer.
 4. A vaso-occlusive device delivery assembly,comprising: a pusher assembly; a tubular connecting member at a distalend of the pusher assembly, the tubular connecting member at leastpartially defining a substantially fluid tight pressure chamber; athermally activated pressure generating material disposed in thepressure chamber; a heat generating member at least partially disposedin the pressure chamber; and a vaso-occlusive device detachably coupledto the pusher assembly, a proximal end of the vaso-occlusive deviceattached to a distal end of the tubular connecting member, wherein aphase change in the pressure generating material, when heated by theheat generating member, occurs that increases a pressure in the pressurechamber, thereby directly causing detachment of the vaso-occlusivedevice from the pusher assembly.
 5. The vaso-occlusive device deliveryassembly of claim 4, wherein the pressure generating material is locatedadjacent to, or in contact with, the heat generating member.
 6. Thevaso-occlusive device delivery assembly of claim 4, wherein the pressuregenerating material comprises a solid.
 7. The vaso-occlusive devicedelivery assembly of claim 6, wherein the pressure generating materialcomprises an inorganic salt hydrate selected from the group consistingof sodium carbonate monohydrate, calcium sulfate dihydrate, calciumsulfate pentahydrate, copper sulfate pentahydrate, and sodiumbicarbonate.
 8. The vaso-occlusive device delivery assembly of claim 4,wherein the heat generating member is a resistive heating coil.
 9. Thevaso-occlusive device delivery assembly of claim 4, the vaso-occlusivedevice comprising an attachment member at a proximal end thereof, theattachment member being frictionally secured to the pusher assembly,wherein a proximal end of the attachment member comprises a distal wallof the pressure chamber, such that the increased pressure in thepressure chamber expels the attachment member from the pusher assembly.10. The vaso-occlusive device delivery assembly of claim 9, the pusherassembly further comprising a resilient retaining member frictionallysecured to the attachment member, wherein the increased pressure deformsthe resilient retaining member.
 11. The vaso-occlusive device deliveryassembly of claim 10, wherein the resilient retaining member is made ofa deformable polymer.
 12. The vaso-occlusive device delivery assembly ofclaim 4, wherein the tubular connecting member comprises a detach zone,such that the increased pressure ruptures the tubular connecting memberin the detach zone, and wherein the detach zone is thermally ormechanically weakened.
 13. The vaso-occlusive device delivery assemblyof claim 4, wherein the heat generated by the heat generating memberraises the temperature of the pressure generating material, such thatthe phase change in the pressure changing material occurs.
 14. Avaso-occlusive device delivery assembly, comprising: a pusher assembly;a tubular connecting member at a distal end of the pusher assembly, thetubular connecting member at least partially defining a substantiallyfluid tight pressure chamber; a thermally activated pressure generatingmaterial disposed in the pressure chamber; a heat generating member atleast partially disposed in the pressure chamber; and a vaso-occlusivedevice detachably coupled to the pusher assembly via the tubularconnecting member, wherein the pressure generating material, when heatedby the heat generating member, increases a pressure in the pressurechamber, thereby rupturing the tubular connecting member and detachingthe vaso-occlusive device from the pusher assembly.
 15. Thevaso-occlusive device delivery assembly of claim 14, wherein thepressure generating material is a single substance that changes stateinto, or otherwise releases at least one of, a liquid or a gas inresponse to heat generated by the heat generating member.
 16. Thevaso-occlusive device delivery assembly of claim 14, wherein the tubularconnecting member comprises a detach zone, such that the increasedpressure ruptures the tubular connecting member in the detach zone, andwherein the detach zone is thermally or mechanically weakened.